Libya ordered the closure of its borders with four of its neighbours on Sunday, as it declared martial law in its vast desert south in the face of mounting unrest, state media reported.

The National Assembly ordered the “temporary closure of the land borders with Chad, Niger, Sudan and Algeria pending new regulations” on the circulation of people and goods, said a decree carried by the official LANA news agency.

“The provinces of Ghadames, Ghat, Obari, Al-Shati, Sebha, Murzuq and Kufra are considered as closed military zones to be ruled under emergency law,” the decree stipulated.

It gave the defence ministry powers to appoint a military governor with authority to arrest fugitives from justice, and detain and deport illegal immigrants.

Assembly member Suad Ganur who represents the city of Sebha, much the largest in the south, said the border closure was a “temporary measure” that would last only “until security has been restored”.

She said there had been an “increase in the flow of illegal immigrants in the expectation of eventual international military action in Mali” against al-Qaeda-linked rebels, who have seized much of the north of the country.

She said the move was also in response to an “upsurge in violence and drug trafficking, and the presence of armed groups that act with complete impunity”.

Prime Minister Ali Zeidan returned on Friday from a regional tour that took him to all four neighbouring countries, promising to reach agreement with them on securing the borders against “terrorists”.

Southern members of the National Assembly had been boycotting it sessions since early this month in protest at the lawlessness plaguing the region.

Almost 200 prisoners escaped from a jail in Sebha on December 4 with the apparent collusion of warders in what deputies described as the “final straw” in ending their patience with the authorities’ security policy.